Prevalence of nine genetic defects in Chinese Holstein cattle

Abstract

Worldwide use of elite sires has caused inbreeding accumulation and high frequencies of genetic defects in dairy cattle populations. In recent years, several genetic defect genes or haplotypes have been identified in Holstein cattle. A rapid and reliable microfluidic chip with Kompetitive allele‐specific PCR (KASP) assay was developed in our previous study for the detection of heterozygotes at eight genetic defect loci of bovine leukocyte adhesion deficiency (BLAD), Brachyspina syndrome (BS), complex vertebral malformation (CVM), Holstein haplotype 1 (HH1), Holstein haplotype 3 (HH3), Holstein haplotype 4 (HH4), Holstein haplotype 5 (HH5) and haplotype for cholesterol deficiency (HCD). This study aimed to extend that assay to include a newly identified genetic defect of Holstein haplotype 6 (HH6) and to estimate the frequencies of carriers for each of the nine genetic defects in six Chinese Holstein herds. Of the 1633 cows, carrier frequencies of the genetic defects were 6.92%, 5.76%, 4.46%, 4.30%, 3.62%, 2.94%, 1.86% and 0.37% for HH1, HH3, CVM, HH5, HCD, BS, HH6 and BLAD, respectively. No carrier was found for HH4. Notably, 27.43% of cows carried at least one genetic defect, while 2.27% and 0.12% of cows carried double and triple genetic defect alleles, respectively. The existence of genetic defects calls for routine molecular testing and effective management of genetic defects by avoiding carrier‐to‐carrier mating in production herds and eliminating or at least reducing the frequency of the defective alleles through marker‐assisted selection in breeding herds.

Multiplex fluorescent amplification‐refractory mutation system PCR method for the detection of 10 genetic defects in Holstein cattle and its comparison with the KASP genotyping assay

“…The carrier frequencies ranged from 0.0% (HH6) to 3.72% (HH3), with 16.12% overall carriers, where 1.03% carried double genetic defects (Table 2). In a previous study, the carrier frequencies ranged from 0% (HH4) to 6.92% (HH1) and the overall carrier frequency was 27.43%, with 2.27% and 0.12% double and triple genetic defects, respectively (Khan et al., 2021). Zhang et al.…”

“…The x-and y-axes show the molecular weight and fluorescence intensity, respectively. (Khan et al, 2021;Yang et al, 2021) and compared with mf-ARMS PCR genotyping results. Conflicting results were validated by Sanger sequencing using sequencing primers (Table S2).…”

“…The 10 genetic defects of 484 randomly sampled Holstein cows were genotyped using the KASP methods (Khan et al., 2021; Yang et al., 2021) and compared with mf‐ARMS PCR genotyping results. Conflicting results were validated by Sanger sequencing using sequencing primers (Table S2).…”

Development of alternative diagnosis of HH1, HH3, HH5 and HCD fertility haplotypes and subfertility syndrome in cattle

“…According to the results of genotyping of 1633 Holstein cows using the KASP method, the frequency of heterozygous carriers was: 6.92%, 5.76%, 4.46%, 4.30%, 3.62%, 2.94%, 1.86% and 0.37%, respectively, for the following fertility haplotypes: HH1, HH3, CVM, HH5, HCD, BS, HH6 and BLAD; however, carriers of the HH4 haplotype were not identified in the study population. It should be noted that 27.43% of cows are carriers of one genetic defect, 2.27% of individuals are simultaneously carriers of two defects, and 0.12% of cows are carriers of three anomalies (Khan et al., 2021).…”

“…Moreover, another study shed light on the genetic landscape of Holstein cattle, reporting even higher percentages of heterozygous carriers of fertility haplotypes. From the DNA analysis of the tested animals, 27.43% were identified as heterozygous carriers of one fertility haplotype, 2.27% simultaneously carried two defects, and a small fraction, 0.12%, exhibited three genetic anomalies(Khan et al, 2021;Kovpak et al, 2022) Id-Lahoucine et al (2023). investigated transmission ratio distortion (TRD) in the bovine genome and identified candidate regions associated with reproduction defects.…”